So that the various internal Cogl*EGL typedefs can be available to
cogl-winsys-kms.c this moves them into cogl-winsys-egl-private.h
Reviewed-by: Rob Bradford <rob@linux.intel.com>
This adds an internal texture_2d constructor that can wrap an EGLImage
as a CoglTexture2D. The plan is to utilize this for texture-from-pixmap
support with EGL as well as creating textures from wayland buffers.